The start() function is a very special function. All of the commands you wish to execute must go inside of the start function, between the curly braces. The commands will be executed in the order that they appear.
The two shapes are congruent, so that means AB corresponds to FG, BC to GH, CD to HI and so on. Basically this means AB = FG and so on. So this means CD = HI. And we know CD = 10 so HI = 10.
